More crypto work in progress...

node/Utils.hpp

@@ -66,6 +66,38 @@ namespace ZeroTier {
 class Utils
 {
 public:
+	/**
+	 * Perform a time-invariant binary comparison
+	 *
+	 * @param a First binary string
+	 * @param b Second binary string
+	 * @param len Length of strings
+	 * @return True if strings are equal
+	 */
+	static inline bool secureEq(const void *a,const void *b,unsigned int len)
+		throw()
+	{
+		const char *p1 = (const char *)a;
+		const char *p2 = (const char *)b;
+		uint64_t diff = 0;
+
+		while (len >= 8) {
+			diff |= (*((const uint64_t *)p1) ^ *((const uint64_t *)p2));
+			p1 += 8;
+			p2 += 8;
+			len -= 8;
+		}
+
+		while (len) {
+			diff |= (uint64_t)(*p1 ^ *p2);
+			++p1;
+			++p2;
+			--len;
+		}
+
+		return (diff == 0ULL);
+	}
+
 	/**
 	 * Delete a file
 	 *